Electromagnetically-actuated electric switches



Oct. 22, 1963 c. E. HAYTER 3,108,208

ELECTROMAGNETICALLY-ACTUATED ELECTRIC SWITCHES I Filed July 17, 1959United States Patent 3,1tl8,203 ELECTROMAGNETHCALLY-ACTUATEI) ELECTRMSWITQHES Charles Ewart Hayter, Oxhey, England, assiguor to RotaxLimited, London, England Filed July 17, 1959, tier. No. 327,768 1 Claim.(Cl. 317-155.5)

This invention relates to electromagnetically-operable electric switchmechanisms of the kind having an actuating electromagnet provided with amain winding and an auxiliary winding.

The object of the invention is to prevent overheating of the mainwinding of the electromagnet as a result of variations in the voltage ofthe energising current.

' The invention comprises in combination a first :elec tromagnet havinga main winding and an auxiliary winding interconnected in series, asecond electromagnet hava single winding connected in parallel with themain and auxiliary windings of the first electromagnet, a main switchhaving an actuating member movable by the first electromagnet to eifeotclosure of the main switch, a second switch connected in parallel withthe auxiliary Winding of the first electromagnet and operable by thesecond electromagnet for short-circuiting the said auxiliary winding,and a third switch connected in series with the winding of the secondelectromagnet and movable to its open position by the actuating memberof the main switch during movement of the said member by the firstelectromagnet.

In the accompanying drawings, FIGURE 1 is :1 diagram illustrating onemode of carrying the invention into effect, and FIGURE 2is a fragmentaryview illustrating diagrammatically how the third switch can be opened bythe actuating member of the main switch.

Referring to FIGURE 1, the part herein referred to as the main switchcomprises a plunger a or other movable member loaded by a spring b andcarrying a contact piece 0 for co-operating with fixed contact pieces din the circuit to be controlled by the switch. The electromagnet foractuating the main switch comprises a pair of windings e, f connected inseries. The winding e (herein referred to as the main winding) is ofconsiderably lower resistance than the other winding (herein referred toas the auxiliary winding) and is designed to be capable of closing themain switch when a given voltage is applied to it.

The auxiliary winding 1 is controlled by a short-circuiting switchcomprising a movable member g and an electromagnet h connected inparallel with the windings of the main switch. The circuit containingthe electromagnet h is controlled by a switch i loaded by a spring 1'and movable to its open position by the movable member of the mainswitch through any convenient means such as that shown in FIGURE 2 inwhich a radial projection a on the movable member a of the main switchis adapted to act on and open the switch i during movement of the saidmember by the first mentioned electromagnet.

The circuit which supplies energising current .to the main switchwindings e, f, and the circuit containing the electromagnet h and switch1 is controlled by a manually or otherwise operable switch k.

3,168,208 Patented Oct. 22, 1963 The arrangement is such that when themain switch is open, the short-circuiting switch g is open, and therelay control switch i is closed. To close the main switch, the switch kin the energising circuit is closed. If a sufiicie-nt voltage exists inthe energising circuit, the immediate eifect is to cause the current inthe electromagnet h to close the short-circuiting switch g. A relativelyheavy current then passes momentarily through the main winding e andcauses the main switch to be closed. With the closing of the main switchthe control switch i is opened, and a relatively small current thenpasses through the main and auxiliary windings for holding the mainswitch closed. On interrupting the energising current the parts revertto their initial condition.

The switch above described is required more particularly where thevoltage of the energising circuit is liable to large variations.Assuming this voltage to be low when the switch k in this circuit isclosed, and assuming also that the auxiliary winding f andshort-circuiting switch g are not provided, the current supplied to themain winding e may be insufficient to close the main switch, butsufiicient, it maintained, to incur a risk of burning out of the saidwinding. But by combining with the winding e, the winding andshort-circuiting switch g, as above described, this risk is obviated, asthe main switch would fail to respond to a low Voltage and theshort-circuiting switch g, It would remain open. In [this case thecurrent supplied to the windings e, f of the main switch, whilstinadequate to close the switch would be insufiicient to incur risk ofexcessive heating of these windings.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

An electromagnetically operable electric switch mechanism comprising incombination a first electromagnet having a main winding and an auxiliarywinding providing an impedance interconnected in series across a sourceof voltage, a second electromagnet having a single winding connected inparallel with the main and auxiliary windings of the firstelectromagnet, a main switch having an actuating member movable by thefirst electromagnet in response to a predetermined fiow of currentthrough the main winding to eliect closure of the main switch, a secondswitch connected in parallel with the auxiliary winding of the firstelectromagnet and operable by the second electromagnet in response to asecond predetermined flow of current through the single winding forshort-circuiting the said auxiliary winding, and a third switchconnected in series with the winding of the second electromagnet andmovable to its open position by the actuating member of the main switchduring movement of the said member by the first electromagnet.

References Cited in the file of this patent UNITED STATES PATENTS954,745 Larsen Apr. 12, 1910 1,810,306 Trofimov June 16, 1931 1,817,431Andersen Aug. 4, 1931 1,875,859 Dowling Sept. 6, 1932

